The present invention relates to a hydrocracking process comprising at least one matrix, an IM-5 zeolite, at least one hydrodehydrogenating metal preferably selected from the group formed by metals from group VIB and group VIII of the periodic table, optionally at least one promoter element selected from the group formed by phosphorous, boron and silicon, optionally at least one group VIIA element, optionally at least one group VIIB element and optionally at least one group VB element. The invention also relates to a catalyst based on IM-5 zeolite, containing at least one hydrodehydrogenating metal selected from the group formed by group VI and group VIII metals, and containing at least one promoter element selected from the group formed by boron and silicon.
Hydrocracking heavy petroleum feeds is a very important refining process which produces lighter fractions such as gasoline, jet fuel and light gas oil from surplus heavy feeds of low intrinsic value, which lighter fractions are needed by the refiner to enable production to be matched to demand. Some hydrocracking processes can also produce a highly purified residue which can constitute an excellent base for oils. The advantage of catalytic hydrocracking over catalytic cracking is that it can provide very good quality middle distillates, jet fuels and gas oils. The gasoline produced has a much lower octane number than that resulting from catalytic cracking.
All catalysts used for hydrocracking are bifunctional, combining an acid function and a hydrogenating function. The acid function is supplied by large surface area supports (150 to 800 m2/g in general) with a superficial acidity, such as halogenated aluminas (in particular fluorinated or chlorinated), combinations of boron and aluminium oxides, amorphous silica-aluminas and zeolites. The hydrogenating function is supplied either by one or more metals from group VIII of the periodic table, or by a combination of at least one metal from group VIB of the periodic table, and at least one group VIII metal.
The equilibrium between the two, acid and hydrogenating, functions is the fundamental parameter which governs the activity and selectivity of the catalyst. A weak acid function and a strong hydrogenating function produces low activity catalysts which generally operate at a high temperature (390xc2x0 C. or above), and at a low supply space velocity (HSV, expressed as the volume of feed to be treated per unit volume of catalyst per hour, and is generally 2 hxe2x88x921 or less), but have very good selectivity for middle distillates. In contrast, a strong acid function and a weak hydrogenating function produces very active catalysts but selectivities for middle distillates are poorer. The search for suitable catalysts thus revolves around the proper selection of each of the functions to adjust the activity/selectivity balance of the catalyst.
Thus one of the great interests of hydrocracking is to have a high degree of flexibility at various levels: flexibility as regards the catalysts used, which provides flexibility in the feeds to be treated and in the products obtained. One parameter which is easily mastered is the acidity of the catalyst support.
The vast majority of conventional hydrocracking catalysts are constituted by low acidity supports such as amorphous silica-aluminas. These systems are more particularly used to produce very high quality middle distillates and again, when their acidity is very low, base oils.
Amorphous silica-aluminas are low acidity supports. Many of the catalysts in the hydrocracking industry are based on silica-alumina associated either with a group VIII metal or, as is preferable when the heteroatomic poison content in the feed to be treated exceeds 0.5% by weight, a combination of sulphides of group VIB and VIII metals. These systems have very good selectivity for middle distillates, and good quality products are formed. The least acid of such catalysts can also produce lubricating bases. The disadvantage of all of such catalytic systems based on an amorphous support is, as has been stated, their low activity.
Catalysts comprising a Y zeolite with structure type FAU, or beta type catalysts have a catalytic activity which is higher than that of amorphous silica-aluminas, but have higher selectivities for light products.
The research carried out by the Applicant on numerous zeolites and microporous crystalline solids have led to the surprising discovery that a catalyst based on an IM-5 zeolite can achieve a catalytic activity and kerosine and gasoline selectivities which are substantially improved over catalysts containing a prior art zeolite.
More precisely, the invention provides a process for hydrocracking hydrocarbon-containing feeds in which the feed to be treated is brought into contact with a catalyst comprising at least one amorphous or low crystallinity matrix of an oxide type, at least one IM-5 zeolite and at least one hydrodehydrogenating element.
The IM-5 zeolite used in the present invention has been described in French patent FR-A-2 754 809. The invention also encompasses any zeolite of the same structure type as that of IM-5 zeolite.
The zeolitic structure, termed IM-5, has a chemical composition with the following formula, expressed in terms of the mole ratios of the oxides for the anhydrous state:
100XO2, mY2O3, pR2/nO
where
m is 10 or less;
p is in the range 0 (excluded) to 20;
R represents one or more cations with valency n;
X represents silicon and/or germanium, preferably silicon;
Y is selected from the group formed by the following elements: aluminium, iron, gallium, boron, and titanium, Y preferably being aluminium; and is characterized by an X ray diffraction diagram, in its as synthesised state, which comprises the peaks shown in Table 1.
The IM-5 zeolite in its hydrogen form, designated H-IM-5, is obtained by calcining step(s) and/or ion exchange step(s) as will be explained below. The H-IM-5 zeolite has an X ray diffraction diagram which comprises the results shown in Table 2.
These diagrams were obtained using a diffractometer and a conventional powder method utilising the Kxcex1line of copper. From the position of the diffraction peaks represented by the angle 2xcex8, the characteristic interplanar distances dhkl of the sample can be calculated using the Bragg equation. The intensity is calculated on the basis of a relative intensity scale attributing a value of 100 to the line representing the strongest peak on the X ray diffraction diagram, and then:
very weak (vw) means less than 10;
weak (w) means less than 20;
medium (m) means in the range 20 to 40;
strong (s) means in the range 40 to 60;
very strong (vs) means more than 60.
The IM-5 zeolite can thus be used in its xe2x80x9cas synthesisedxe2x80x9d form and in forms obtained by dehydration and/or calcining and/or ion exchange. The expression xe2x80x9cin its as synthesised formxe2x80x9d means the product obtained by synthesis and washing with or without drying or dehydration. In its xe2x80x9cas synthesisedxe2x80x9d form, the IM-5 zeolite can comprise a cation of metal M, which is an alkali, in particular sodium, and/or ammonium, and it can comprise organic nitrogen-containing cations such as those described below or their decomposition products, or precursors thereof. These organic nitrogen-containing cations are designated here by the letter Q, which also includes decompositon products and precursors of said nitrogen-containing organic cations.
The calcined forms of the IM-5 zeolite contain no organic nitrogen-containing compounds, or a lower quantity than in the xe2x80x9cas synthesised formxe2x80x9d, provided that the majority of the organic substance has been eliminated, generally by a heat treatment consisting of burning the organic substance in the presence of air, the hydrogen ion (H+) thus forming the other cation.
Of the IM-5 zeolite forms which can be obtained by ion exchange, the ammonium form (NH4+) is important as it can readily be converted into the hydrogen form by calcining. The hydrogen form and forms containing metals introduced by ion exchange will be described below.
In some cases, the fact that the zeolite of the invention is subjected to the action of an acid can give rise to partial or complete elimination of a base element such as aluminium, as well as generation of the hydrogen form. This may constitute a means of modifying the composition of the substance after it has been synthesised.
IM-5 zeolite in its hydrogen form (acid form), termed H-IM-5, is produced by calcining and ion exchange as will be described below.
The IM-5 zeolite can also be used at least partially in its H+ form (as defined above) or in its NH4+ form or in its metallic form, said metal being selected from the group formed by groups IA, IB, IIA, IIB, IIIA, IIIB (including the rare earths), VIII, Sn, Pb and Si, preferably at least partially in its H+ form or at least partially in its metal form.
Preferably, the IM-5 zeolite is at least partially in its acid form (and preferably completely in its H form) or partially exchanged with metal cations, for example alkaline-earth metal cations.
The IM-5 zeolites which form part of the composition of the invention are used with the silicon and aluminium contents obtained on synthesis.
It is also possible to use dealuminated IM-5 zeolite, which is described in French patent FR-A-2 758 810, and which has an overall Si/Al atomic ratio of more than 5, preferably more than 10, more preferably more than 15, and still more preferably in the range 20 to 400.
The IM-5 zeolite is advantageously at least partially and preferably almost completely in its acid form.
The Na/Al atomic ratio is generally less than 0.45, preferably less than 0.30 and still more preferably less than 0.15.
To prepare the dealuminated IM-5 zeolite of the invention, at least two dealumination methods can be used starting from as synthesised IM-5 zeolite comprising an organic structuring agent. They are described below. However, any other method which is known to the skilled person can also be used.
The first method, direct acid attack, comprises a first calcining step carried out in a stream of dry air, at a temperature which is generally in the range 450xc2x0 C. to 550xc2x0 C., which eliminates the organic structuring agent present in the micropores of the zeolite, followed by a step in which the zeolite is treated with an aqueous solution of a mineral acid such as HNO3 or HCl or an organic acid such as CH3CO2H. This latter step can be repeated as many times as is necessary to obtain the desired degree of dealumination. Between these two steps, one or more ion exchange steps can be carried out using at least one NH4NO3 solution, to at least partially and preferably almost completely eliminate the alkaline cation, in particular sodium. Similarly, at the end of the direct acid attack dealumination step, one or more optional ion exchange steps can be carried out using at least one NH4NO3 solution to eliminate residual alkaline cations, in particular sodium.
In order to obtain the desired Si/Al ratio, the operating conditions must be correctly selected; the most critical parameters in this respect are the temperature of the treatment with the aqueous acid solution, the concentration of the latter, its nature, the ratio between the quantity of acid solution and the mass of the treated zeolite, the treatment period and the number of treatments carried out.
The second method, heat treatment (in particular using steam, by steaming)+acid attack, comprises firstly calcining in a stream of dry air at a temperature which is generally in the range 450xc2x0 C. to 550xc2x0 C., to eliminate the organic structuring agent occluded in the micropores of the zeolite. The solid obtained then undergoes one or more ion exchanges using at least one NH4NO3 solution, to eliminate at least a portion and preferably practically all of the alkaline cation, in particular sodium, present in the cationic position of the zeolite. The zeolite obtained then undergoes at least one framework dealumination cycle comprising at least one heat treatment which is optionally and preferably carried out in the presence of steam, at a temperature which is generally in the range 550xc2x0 C. to 900xc2x0 C., and optionally followed by at least one acid attack using an aqueous solution of a mineral or organic acid. The conditions for calcining in the presence of steam (temperature, steam pressure and treatment period), also the post-calcining acid attack conditions (attack period, concentration of acid, nature of acid used and the ratio between the volume of the acid and the mass of zeolite) are adapted so as to obtain the desired level of dealumination. For the same reason, the number of heat treatment-acid attack cycles can be varied.
The framework dealumination cycle, comprising at least one heat treatment step, optionally and preferably carried out in the presence of steam, and at least one attack step of the IM-5 zeolite carried out in an acid medium, can be repeated as often as is necessary to obtain the dealuminated IM-5 zeolite having the desired characteristics. Similarly, following the heat treatment, optionally and preferably carried out in the presence of steam, a number of successive acid attacks can be carried out using different acid concentrations.
In a variation of this second calcining method, heat treatment of the IM-5 zeolite containing the organic structuring agent can be carried out at a temperature which is generally in the range 550xc2x0 C. to 850xc2x0 C., optionally and preferably in the presence of steam. In this case, the steps of calcining the organic structuring agent and dealumination of the framework are carried out simultaneously. The zeolite is then optionally treated with at least one aqueous solution of a mineral acid (for example HNO3 or HCl) or an organic acid (for example CH3CO2H). Finally, the solid obtained can optionally be subjected to at least one ion exchange step using at least one NH4NO3 solution, to eliminate practically all of the alkaline cations, in particular sodium, present in the cationic position in the zeolite.
The zeolite is then used with the Si/Al ratio obtained after dealumination.
The catalyst also comprises a hydrogenating function which is generally ensured by at least one metal selected from the group formed by metals from group VIB and group VIII of the periodic table.
The catalyst of the present invention can comprise an element from group VIII such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium or platinum. Preferred group VIII elements are non noble metals such as iron, cobalt and nickel. The catalyst of the invention can comprise a group VIB element, preferably tungsten and molybdenum. Advantageously, combinations of at least one non noble metal from group VIII and at least one group VIB metal are used. Preferred combinations are: nickel- molybdenum, cobalt- molybdenum, iron-molybdenum, iron-tungsten, nickel-tungsten, cobalt-tungsten. Preferred combinations are: nickel-molybdenum, cobalt-molybdenum and nickel-tungsten. It is also possible to use combinations of three elements, for example nickel-cobalt-molybdenum.
The catalyst of the present invention also comprises at least one porous amorphous or low crystallinity oxide type mineral matrix. Non limiting examples are alumina, silica and silica-alumina, clays (for example natural clays such as kaolin or bentonite), magnesia, titanium oxide, boron oxide, zirconia, aluminium phosphates, titanium phosphates, zirconium phosphates, charcoal. Aluminate can also be selected. Preferably, matrices containing alumina are used in any of its forms which are known to the skilled person, more preferably aluminas, for example gamma alumina.
In one implementation of the invention, the catalyst comprises at least one promoter element selected from the group formed by boron, silicon and phosphorous. A preferred catalyst comprises boron and/or silicon as the promoter element, more preferably boron and silicon.
The catalyst can optionally comprise at least one group VIIA element, preferably chlorine and fluorine, and optionally at least one group VIIB element (preferably Mn).
The catalyst can optionally comprise at least one group VB element (Ta, Nb, V), preferably niobium.
When the catalyst contains silicon, the silicon is introduced onto the support of the invention as a promoter. The silicon is primarily located on the support matrix and can be characterized by techniques such as a Castaing microprobe (distribution profile of the various elements), transmission electron microscopy coupled with X ray analysis of the catalyst components, or by establishing a distribution map of the elements present in the catalyst using an electron microprobe.
The invention also provides a catalyst comprising at least one amorphous or low crystallinity oxide type matrix, an IM-5 zeolite, at least one hydrodehydrogenating element selected from the group formed by group VIII metals and group VIB metals, and at least one promoter element selected from the group formed by boron and silicon. Advantageously, the catalyst also comprises phosphorous. Optionally, the catalyst can also comprise at least one group VIIB element and/or at least one group VIIA element and/or at least one group VB element. These catalysts are advantageously used for hydrocracking.
The catalyst of the present invention generally comprises, as a % by weight with respect to the total catalyst mass:
0.1% to 60%, preferably 0.1% to 50%. More preferably 0.1% to 40% of at least one hydrodehydrogenating metal, advantageously selected from the group formed by group VIB and group VIII metals;
0.1% to 99%, preferably 1% to 98%, of at least one porous amorphous or low crystallinity oxide type mineral matrix;
said catalyst also comprising 0.1% to 99.8%, preferably 0.1% to 90%, preferably 0.1% to 80%, still more preferably 0.1% to 60%, of IM-5 zeolite;
said catalyst optionally containing:
0 to 20%, advantageously 0.1% to 20%, preferably 0.1% to 15%, still more preferably 0.1% to 10%, of at least one promoter element selected from the group formed by silicon, boron and phosphorous, not including the silicon which is optionally contained in the IM-5 zeolite;
0 to 20%, advantageously 0.1% to 20%, preferably 0.1% to 15%, still more preferably 0.1% to 10%, of at least one element selected from group VIIA, preferably fluorine;
0 to 20%, advantageously 0.1% to 20%, preferably 0.1% to 15%, still more preferably 0.1% to 10%, of at least one element selected from group VIIB, preferably manganese;
0 to 60%, preferably 0.1% to 60%, advantageously 0.1% to 50%, still more preferably 0.1% to 40%, of at least one element selected from group VB.
A preferred catalyst comprises, in % by weight with respect to the total catalyst mass:
0.1% to 99.7% of IM-5 zeolite; p1 0.1% to 60% of at least one hydrodehydrogenating metal;
0. 1% to 99% of at least one matrix;
0. 1% to 20% of boron and/or silicon;
0 to 20% of phosphorous, the sum of the quantities of boron and/or phosphorous and/or silicon being at most 20%;
0 to 20% of at least one group VIIA element;
0 to 20% of at least one group VIIB element;
0 to 60% of at least one group VB element.
This catalyst can also comprise all the characteristics described above: the preferred ranges of values for the components, the preferred components, and optional groups VIIA, VIIB and VB.
The group VIB metals, group VIII metals, group VIIB metals and group VB metals of the catalyst of the present invention can also be present completely or partially in the form of the metal and/or oxide and/or sulphide.
The catalyst can be prepared by any method which is known in the art. Advantageously, it is obtained by mixing the matrix and the zeolite then forming the mixture. The hydrogenating element is introduced during mixing, or preferably after forming.
Forming can be carried out by extrusion, pelletization, by the oil drop method, by rotating plate granulation or using any other method which is well known to the skilled person. Forming is followed by calcining; the hydrogenating element is introduced before or after calcining. The preparation is completed by calcining at a temperature of 250xc2x0 C. to 600xc2x0 C.
One preferred method of the present invention consists of mixing the IM-5 zeolite powder in a moist alumina gel for several tens of minutes, then passing the paste obtained through a die to form extrudates with a diameter in the range 0.4 to 4 mm.
The hydrogenating function can be introduced in part only (for example in the case of combinations of oxides of group VIB and VIII metals) or in its entirety on mixing the zeolite, i.e., the IM-5 zeolite, with the gel of the oxide selected as the matrix.
The hydrogenating function can also be introduced by one or more ion exchange operations carried out on the calcined support constituted by an IM-5 zeolite, dispersed in the selected matrix, using solutions containing precursor salts of the selected metals.
The hydrogenating function can also be introduced by one or more operations for impregnating the formed and calcined support, using a solution containing at least one precursor of at least one oxide of at least one metal selected from the group formed by group VIII metals and group VIB metals, the precursor(s) of at least one oxide of at least one group VIII metal preferably being introduced after those of group VIB or at the same time as the latter, if the catalysts contain at least one group VIB metal and at least one group VIII metal.
When the catalyst contains at least one group VIB element, for example molybdenum, it is possible, for example, to impregnate the catalyst with a solution containing at least one group VIB element, dry then calcine. Molybdenum impregnation can be facilitated by adding phosphoric acid to solutions of ammonium paramolybdate, which thus also introduces the phosphorous function to promote the catalytic activity.
In a preferred implementation of the invention, the catalyst contains, as a promoter, at least one element selected from silicon, boron and phosphorous. These elements are introduced into a support already containing at least one IM-5 zeolite, at least one matrix as defined above, and preferably also containing at least one metal selected from the group formed by group VIB and group VIII metals.
When the catalyst contains boron and/or silicon and/or phosphorous and optionally an element selected from group VIIA, halogen ions, optionally at least one element selected from group VIIB and optionally at least one element selected from group VB, these elements can also be introduced into the catalyst at various stages of the preparation and in various manners.
The matrix is preferably impregnated using the xe2x80x9cdryxe2x80x9d impregnation method which is well known to the skilled person. Impregnation can be carried out in a single step using a solution containing all of the constituent elements of the final catalyst.
The P, B, Si and the element selected from group VIIA halide ions can be introduced into the calcined precursor by one or more impregnation operations using an excess of solution.
When the catalyst contains boron, one preferred method of the invention consists of preparing an aqueous solution of at least one boron salt such as ammonium biborate or ammonium pentaborate in an alkaline medium and in the presence of hydrogen peroxide and carrying out dry impregnation, in which the pore volume of the precursor is filled with the solution containing boron.
When the catalyst contains silicon, a silicone type silicon compound is used.
When the catalyst contained boron and silicon, the boron and silicon can also be deposited simultaneously using a solution containing a boron salt and a silicone type silicon compound. Thus where the precursor is a nickel-molybdenum type catalyst supported on a support containing alumina and IM-5 zeolite, for example, it is possible to impregnate this precursor with an aqueous solution of ammonium biborate and Rhodorsil E1P silicone from Rhxc3x4ne Poulenc, to dry at 80xc2x0 C., for example, impregnate with an ammonium fluoride solution, then dry at 80xc2x0 C., for example, followed by calcining, preferably in air in a traversed bed, for example at 500xc2x0 C. for 4 hours.
When the catalyst contains at least one group VIIA element, preferably fluorine, it is possible to impregnate the catalyst with an ammonium fluoride solution, to dry at 80xc2x0 C. for example, followed by calcining, preferably in air in a traversed bed, for example at 500xc2x0 C. for 4 hours.
Other impregnation sequences can be used to obtain the catalyst of the invention.
When the catalyst contains phosphorous, it is possible to impregnate the catalyst with a solution containing phosphorous, to dry, then to calcine.
When the elements contained in the catalyst, i.e., at least one metal selected from the group formed by group VIII and group VIB metals, optionally boron, silicon, phosphorous, at least one group VIIA element, at least one group VIIB element, at least one group VB element, are introduced in a number of steps for impregnating the corresponding precursor salts, an intermediate step for drying the catalyst is generally carried out at a temperature which is generally in the range 60xc2x0 C. to 250xc2x0 C. and an intermediate catalyst calcining step is generally carried out at a temperature in the range 250xc2x0 C. to 600xc2x0 C.
To finish the catalyst preparation, the moist solid is left in a moist atmosphere at a temperature in the range 10xc2x0 C. to 80xc2x0 C., then the moist solid obtained is dried at a temperature in the range 60xc2x0 C. to 150xc2x0 C., and finally the solid obtained is calcined at a temperature in the range 150xc2x0 C. to 800xc2x0 C.
A preparation process consists of carrying out the following operations:
a) preparing a solid termed the precursor, comprising at least the following compounds: at least one matrix, at least one IM-5 zeolite, optionally at least one element selected from the group formed by group VIB and group VIII elements, optionally at least one promoter element selected from the group boron and silicon, optionally phosphorous, and optionally at least one group VIIA element, the whole preferably having been formed;
b) calcining the dry solid obtained in step a) at a temperature of at least 150xc2x0 C.;
c) if necessary, impregnating the solid precursor obtained from step b) with at least one solution containing at least one element from group VIIB, VB, VIII, VIB or VIIA;
d) leaving the moist solid in a moist atmosphere at a temperature in the range 10xc2x0 C. to 1 20xc2x0 C.;
e) drying the moist solid obtained in step d) at a temperature in the range 60xc2x0 C. to 150xc2x0 C.
Sources of group VIB elements which can be used are well known to the skilled person. Examples of molybdenum and tungsten sources are oxides and hydroxides, molybdic acids and tungstic acids and their salts, in particular ammonium salts such as ammonium molybdate, ammonium heptamolybdate, ammonium tungstate, phosphomolybdic acid, phosphotungstic acid and their salts, silicomolybdic acid, silicotungstic acid and their salts. Preferably, oxides and ammonium salts are used, such as ammonium molybdate, ammonium heptamolybdate and ammonium tungstate.
The sources of the group VIII elements which can be used are well known to the skilled person. Examples of sources of non noble metals are nitrates, sulphates, phosphates, halides, for example chlorides, bromides and fluorides, and carboxylates, for example acetates and carbonates. Examples of sources of noble metals are halides, for example chlorides, nitrates, acids such as chloroplatinic acid, and oxychlorides such as ammoniacal ruthenium oxychloride.
The preferred phosphorous source is orthophosphoric acid H3PO4, but its salts and esters such as ammonium phosphates are also suitable. Phosphorous can, for example, be introduced in the form of a mixture of phosphoric acid and a basic organic compound containing nitrogen, such as ammonia, primary and secondary amines, cyclic amines, pyridine group compounds, quinolines, and pyrrole group compounds.
A variety of silicon sources can be used. Examples are ethyl orthosilicate Si(OEt)4, siloxanes, polysiloxanes, silicones and halogenated silicates such as ammonium fluorosilicate (NH4)2SiF6 or sodium fluorosilicate Na2SiF6.
Silicomolybdic acid and its salts, and silicotungstic acid and its salts can also advantageously be used. Silicon can be added, for example, by impregnation using ethyl silicate in solution in a water/alcohol mixture. Silicon can also be added, for example, by impregnation using a silicone type silicon compound suspended in water.
The boron source can be boric acid, preferably orthoboric acid H3BO3, ammonium biborate or pentaborate, boron oxide, or boric esters. Boron can, for example, be introduced in the form of a mixture of boric acid, hydrogen peroxide and a basic organic compound containing nitrogen, such as ammonia, primary and secondary amines, cyclic amines, pyridine group compounds, quinolines, and pyrrole group compounds. Boron can, for example, be introduced using a solution of boric acid in a water/alcohol mixture.
Sources of group VIIA elements which can be used are well known to the skilled person. As an example, fluoride anions can be introduced in the form of hydrofluoric acid or its salts. Such salts are formed with alkali metals, ammonium or an organic compound. In the latter case, the salt is advantageously formed in the reaction mixture by reacting the organic compound with hydrofluoric acid. It is also possible to use hydrolysable compounds which can liberate fluoride anions in water, such as ammonium fluorosilicate (NH4)2SiF6, silicon tetrafluoride SiF4 or sodium fluorosilicate Na2SiF6. Fluorine can be introduced, for example, by impregnating an aqueous hydrofluoride solution or ammonium fluoride.
Sources of group VIIB elements which can be used are well known to the skilled person. Preferably, ammonium salts, nitrates and chlorides are used.
Sources of the group VB element which can be used are well known to the skilled person. Examples of niobium sources are oxides such as diniobium pentoxide Nb2O5, niobic acid Nb2O5.H2O, niobium hydroxides and polyoxoniobates, niobium alkoxides with formula Nb(OR1)3 where R1 is an alkyl radical, niobium oxalate NbO(HC2O4)5, and ammonium niobate. Preferably, niobium oxalate or ammonium niobate are used.
Niobium impregnation can be facilitated by adding oxalic acid and optionally ammonium oxalate to niobium oxalate solutions. Other compounds can be used to improve solubility and facilitate niobium impregnation, as is well known to the skilled person.
At least part of the catalysts obtained, which are in the oxide form, can be placed in the metallic or sulphide form.
The catalysts obtained in the present invention are formed into grains of different shapes and dimensions. They are generally used in the form of cylindrical or polylobed extrudates such as bilobes, trilobes, or polylobes with a straight or twisted shape, but they can also be produced and used in the form of compressed powder, tablets, rings, beads or wheels. The specific surface area is measured by nitrogen adsorption using the BET method (Brunauer, Emmett, Teller, J. Am. Chem. Soc., vol. 60, 309-316 (1938)) and is in the range 50 to 600 m2/g, the pore volume measured using a mercury porisimeter is in the range 0.2 to 1.5 cm3/g and the pore size distribution may be unimodal, bimodal or polymodal.
The catalysts obtained in the present invention are used for hydrocracking hydrocarbon feeds such as petroleum cuts. The feeds used in the process are gasolines, kerosines, gas oils, vacuum gas oils, atmospheric residues, vacuum residues, atmospheric distillates, vacuum distillates, heavy fuels, oils, waxes and paraffins, spent oil, deasphalted residues or crudes, feeds from thermal or catalytic conversion processes, and their mixtures. They contain heteroatoms such as sulphur, oxygen and nitrogen and possibly metals.
The catalysts obtained are advantageously used for hydrocracking, in particular of vacuum distillate type heavy hydrocarbons, deasphalted residues or hydrotreated residues or the like. The heavy cuts are preferably constituted by at least 80% by volume of compounds with a boiling point of at least 350xc2x0 C., preferably in the range 350xc2x0 C. to 580xc2x0 C. (i.e., corresponding to compounds containing at least 15 to 20 carbon atoms). They generally contain heteroatoms such as sulphur and nitrogen. The nitrogen content is usually in the range 1 to 5000 ppm by weight and the sulphur content is in the range 0.01% to 5% by weight.
The catalyst of the present invention can advantageously be used for hydrocracking vacuum distillate type cuts which are highly charged with sulphur and nitrogen.
The catalysts of the present invention preferably undergo sulphurisation to transform at least part of the metallic species to the sulphide before bringing them into contact with the feed to be treated. This activation treatment by sulphurisation is well known to the skilled person and can be carried out using any method already described in the literature, i.e., either in the reactor or ex-situ.
One conventional sulphurisation method which is well known to the skilled person consists of heating in the presence of hydrogen sulphide (pure or, for example, in a stream of a hydrogen/hydrogen sulphide mixture or a nitrogen/hydrogen sulphide mixture) to a temperature in the range 150xc2x0 C. to 800xc2x0 C., preferably in the range 250xc2x0 C. to 600xc2x0 C., generally in a traversed bed reaction zone.
The hydrocracking conditions such as temperature, pressure, hydrogen recycle ratio, and hourly space velocity, can vary widely depending on the nature of the feed, the quality of the desired products and the facilities available to the refiner. The temperature is generally over 200xc2x0 C. and usually in the range 250xc2x0 C. to 480xc2x0 C. The pressure is over 0.1 MPa and usually over 1 MPa. The quantity of hydrogen is a minimum of 50 liters of hydrogen per liter of feed and usually in the range 80 to 5000 liters of hydrogen per liter of feed. The hourly space velocity is generally in the range 0.1 to 20 volumes of feed per volume of catalyst per hour.
In a first implementation, or partial hydrocracking, also known as mild hydrocracking, the degree of conversion is below 55%. The catalyst of the invention is thus used at a temperature which is generally 230xc2x0 C. or more, preferably 300xc2x0 C., generally at most 480xc2x0 C., and usually in the range 350xc2x0 C. to 450xc2x0 C. The pressure is generally over 2 MPa and preferably 3 MPa, less than 12 MPa and preferably less than 10 MPa. The quantity of hydrogen is a minimum of 100 normal liters of hydrogen per liter of feed and usually in the range 200 to 3000 normal liters of hydrogen per liter of feed. The hourly space velocity is generally in the range 0.1 to 10 hxe2x88x921. Under these conditions, the catalysts of the present invention have better activities for conversion, hydrodesulphuration and hydrodenitrogenation than commercially available catalysts.
In a second implementation, the process is carried out in two steps, the catalyst of the present invention being used for partial hydrocracking, advantageously under moderate hydrogen pressure conditions, of cuts such as vacuum distillates containing high sulphur and nitrogen contents which have already been hydrotreated. In this hydrocracking mode, the degree of conversion is below 55%. In this case, the petroleum cut is converted in two steps, the catalysts of the invention being used in the second step. The catalyst of the first step can be any hydrotreatment catalyst which is known in the art. This hydrotreatment catalyst advantageously comprises a matrix, preferably alumina-based, and at least one metal with a hydrogenating function. The hydrotreatment function is ensured by at least one metal or metal compound, used alone in combination, selected from group VIII and group VIB metals, such as nickel, cobalt, molybdenum or tungsten in particular. Further, this catalyst can optionally contain phosphorous and optionally boron.
The first step is generally carried out at a temperature of 350-460xc2x0 C., preferably 360-450xc2x0 C.; the pressure is at least 2 MPa, preferably at least 3 MPa; and the hourly space velocity is 0.1-5 hxe2x88x921, preferably 0.2-2 hxe2x88x921, with a quantity of hydrogen at least 100 Nl/Nl of feed, preferably 260-3000 Nl/Nl of feed.
In the conversion step using the catalyst of the invention (or second hydrocracking step), the temperatures are generally 230xc2x0 C. or more and usually in the range 300xc2x0 C. to 480xc2x0 C., preferably in the range 330xc2x0 C. to 450xc2x0 C. The pressure is generally at least 2 MPa, preferably at least 3 MPa; it is less than 12 MPa and preferably less than 10 MPa. The quantity of hydrogen is a minimum of 100 l/l of feed and usually in the range 200 to 3000 l/l of feed.
The hourly space velocity is generally in the range 0.15 to 10 hxe2x88x921. Under these conditions, the catalysts of the present invention have better activities for conversion, hydrodesulphuration, and hydrodenitrogenation and a better selectivity for middle distillates than commercially available catalysts. The service life of the catalysts is also improved in the moderate pressure range.
In a further implementation carried out in two steps, the catalyst of the present invention can be used for hydrocracking under high hydrogen pressure conditions of at least 5 MPa. The treated cuts are, for example, vacuum distillates containing high sulphur and nitrogen contents which have already been hydrotreated. In this hydrocracking mode, the degree of conversion is over 55%. In this case, the petroleum cut conversion process is carried out in two steps, the catalyst of the invention being used in the second step.
The catalyst of the first step can be any hydrotreatment catalyst which is known in the art. This hydrotreatment catalyst advantageously comprises a matrix, preferably alumina-based, and at least one metal with a hydrogenating function. The hydrogenating function is ensured by at least one metal or metal compound, used alone or in combination, selected from group VIII and group VIB metals, such as nickel, cobalt, molybdenum and tungsten in particular. Further, this catalyst can optionally contain phosphorous and optionally boron.
The first step is generally carried out at a temperature of 350-460xc2x0 C., preferably 360-450xc2x0 C.; the pressure is over 3 MPa; the hourly space velocity is 0.1-5 hxe2x88x921, preferably 0.2-2 hxe2x88x921; and the quantity of hydrogen is at least 100 Nl/Nl of feed, preferably 260-3000 Nl/Nl of feed.
For the conversion step using the catalyst of the invention (or second step), the temperatures are generally 230xc2x0 C. or more, usually in the range 300xc2x0 C. to 480xc2x0 C., preferably in the range 300xc2x0 C. to 440xc2x0 C. The pressure is generally over 5 MPa, preferably over 7 MPa. The quantity of hydrogen is a minimum of 100 l/l of feed, usually in the range 200 to 3000 l/l of hydrogen per liter of feed. The hourly space velocity is generally in the range 0.15 to 10 hxe2x88x921.
Under these conditions, the catalysts of the present invention have better activity for conversion and better selectivity for middle distillates than for commercially available catalysts, even though the zeolite contents are considerably lower than those of commercially available catalysts.